Just over two months ago, Crystal Palace were in a real mess. The Eagles found themselves 19th in the Premier League, looked short of ideas and were in serious danger of being left behind in the race to stay up. Even Sam Allardyce, the man who has never been relegated, was struggling to reverse any sort of momentum in Palace’s favour.

The crux of his side’s problems was the defence. After 25 games, Palace had conceded 46 goals—the joint-most in the league, with set pieces being a particular Achilles heel that kept spoiling any progress made by the forwards at the other end of the pitch. Allardyce is known not only for his ability to drag teams to survival, but also for his emphasis on defensive organisation. It is the centre point of the way he approaches the game and he aims to build his teams around just that. Yet at Palace, it became apparent that he did not quite have the personnel to improve the Eagles’ struggling defence.

Meanwhile, over on Merseyside, Liverpool defender Mamadou Sakho was looking for a new club. During the Reds’ pre-season tour, the Frenchman was sent home by manager Jürgen Klopp for being late for a team flight, a medical treatment session and a team meal. Consequently, Sakho was demoted from first-team duties.

Allardyce then swept in as soon as he could. He secured the signing of Sakho on a loan deal until the end of the season and saw him as just the man to help improve Palace’s defensive crisis. And four games into his Palace career, the impact that Sakho has had on his team’s fortunes has been massive.

Since Sakho’s debut against Middlesborough on the 25th February, Palace have conceded just one goal, and that was against likely champions-to-be Chelsea. Sakho has been instrumental in that run, with no Palace defender winning a higher percentage of aerial duels than the 27-year-old, who is also yet to give away a foul this season.

At Stamford Bridge on Saturday, Sakho was again monumental. The big Frenchman made nine clearances—the most on either side—and seven ball recoveries. In addition, he made five interceptions and proved to be the leader in Palace’s defence after captain Scott Dann went off injured after just 13 minutes.

Sakho’s display against Chelsea was symbolic of his impact on Palace’s turnaround in form. And after the Eagles’ 1-0 win over Watford two weeks before, it was clear how important to the team he had become.

Amid the compliments about his defending, since his time in the Premier League, Sakho has received criticism for not being good enough on the ball. Yet during his spell at Palace, he has shown vast improvement at passing out from the back; a feature now so important for defenders in the modern game. Since his debut, the defender has completed more passes from open play than any other Palace player.

What’s more, Sakho has completed more passes from open play than any other Palace player. He averages 25 passes per game, with an 83% passing accuracy. And to prove how keen he has become at passing out from defence, 79.8% of his passes have gone forward. He is fast becoming the all-round defender.

And Allardyce knows only too well how much of an influence Sakho has had on his side. “The lift he has given us defensively in the two games he has played has been exceptionally good,” the Palace boss said after a 2-0 win at West Brom in March.

It, therefore, remains a mystery as to why Liverpool keep ignoring Sakho. The Reds’ defensive woes have arguably cost them a real challenge for the league title this season. Joel Matip has impressed but has suffered from injury problems, and fellow centre-backs Dejan Lovren and Ragnar Klavan have failed to deliver on a consistent basis.

Continuous problems in the centre of defence are having a debilitating effect on Klopp’s side’s chance of progressing into a title-winning team. Liverpool have even had to resort to playing holding midfielder Lucas Leiva in the heart of their defence this season.

Klopp has made it clear that he does not tolerate ill-discipline both on and off the field but you would be forgiven to think how much of a difference Sakho would make to his side if the defender’s summer misdemeanours were forgiven. Not only would he provide better defensive solidarity, he could also form part of Liverpool’s build up play, given the improvement in his passing this season.

Perhaps Klopp is refusing to get carried away after four games of Sakho at Palace and is instead waiting to see if the Frenchman can guide Crystal Palace to Premier League safety by the end of the season, before making any decisions regarding reintegrating him back into the Liverpool team.

Regardless, there is little doubt that Sakho will have plenty of suitors when he finishes his loan spell at Selhurst Park in the summer. And although Allardyce is once again close to doing what he does best—keeping teams up—it has been Sakho who has been the real reason why Palace have gone from no-hopers to a side which finally means business again.